Method of making copper molds



Sept 15, 1936. H; RCE 2,054,635

METHOD OF MAKING COPPER MOLDS 7 Filed May 10, 1934 2 Sheets-Sheet 2HIIIIHM ATTORN EYS Registered Sept. 15, 1936 UNITED STATES PATENT OFFICEMETHOD OF MAKING COPPER MOLDS Application May 10, 1934, Serial No.724,836

'lClaims.

This invention relates to vertical casting molds and to an improvedmethod of' making such molds y from copper and copper alloys.

The invention provides copper molds admirably suited for copper andother non-ferrous metal alloys such as, for example, brass, bronze,nickel silver, monel metal and the like as well as ferrous 'metals andalloys such as ordinary carbon steels, stainless steels, rustless ironand the like which have relatively high melting points.

In accordance with the invention, molds may be made which will producecastings of any desirable cross sectional shapes whether square,rectangular, circular or irregular and likewise of any desirable depth.

The invention is particularly suited to the production of castings whichare not of uniform cross sectional area and especially vertical castbars of electrolytic copper, oxygen-free copper,

2o deoxidized copper and copper alloys.

Generally stated, the invention contemplates a two step process ofmaking molds mechanically direct from metal in suitable form, such as acast block, cake or billet of the desired conformation without secondarymachining or finishing processes.

More particularly, the invention comprises the piercing of a block, cakeor billet of copper, while in a heated condition and while held in areceptacle of appropriate size, with a tool or-plunger adapted to make acavity or recess in the block. cake or billet of predeterminedconformation and. dimensions, and then subjecting theproduct to a colddrawing operation over a tool or mandrel whereby the dimensions of theinterior cavity or recess are brought to the precise and exact dimen- Vsionsdesired.

The invention also consists in certain new and original features ofconstruction and combina- 4g tions of parts hereinafter set forth andclaimed. Although the novel features which are believed to' becharacteristic of this invention will be particularly pointed out in theclaims appended hereto,the invention itself, as to its objects andadvantages, and the manner in which it may be carried out, may be betterunderstood by referring to the following description taken in connectionwith the accompanying drawings forming a part thereof, in which Fig. 1is a diagrammatical representation of piercing press;

Fig. 2 is a diagrammatic representation of the press with the plunger atthe end of a piercing stroke;

Fig. 3 is a side view of a pierced billet;

for convenience, but they are intended to beas generic in theirapplication as the art will permit.

Like reference characters denote like parts in 15 the several figures ofthe drawings.

In, the drawings accompanying and forming part of this specification,certain specific disclosure of the invention is made for purposes ofexplanation, but it will be understood that the 20 details may bemodified in various respects without departure from the broad aspect ofthe invention.

Referring now more particularly to the drawings, a piercing press isdiagrammatically repre- 28 sented in Figs. 1 and 2 in which a receptacleII is adapted to hold a hot copper b'illet l1 suitable for piercing. Adouble-acting ram lZis adapted to apply pressure to the piercing tool orplunger I 4 section to that of plunger ll.

In the piercing operation, the hot billet I1 is placed in the receptacleII and the ram is operated to force the plunger 14 through the hotbillet. A core I0 is thus pierced from the center of the billet (Fig.2). nally slightly smaller than the interior of the receptacle wherebyit may expand slightly during the piercing operation to yield thedimensions desired in the pierced billet. The'ram is then reversed towithdraw the plunger from the billet. 45 Usual suitable means areprovided to withdraw the billet fromthe receptacle.

The pierced billet or mold stock thus formed is shown in Figs. 3 and 4.In this example, the billet may be of circular cross section with a uni-50 form square hole extending axially throughout v its length. It maybeof any length or shape desired within the limits of the piercingpress.

Any oxide formed on the mold stock by the hot piercing may be removedpreferably by pickling 55 The billet is origiin a suitable reagent suchas, for example, sulphuric acid solution, with subsequent water washingto remove traces of the pickling reagent. The square hole may still besomewhat roughened about its edges due to the action of the piercingpress, however, and the stock may contain other flaws and cavitiesformed during the casting of the billet.

The next step not only eliminates this roughness, forming a smoothsurface within the hole and eliminating the cavities but also shapes thestock into the configuration desired in the finished mold. This isaccomplished by subjecting the stock to one or more cold draws over oneor more smooth steel'mandrels, the last mandrel having the desired shapeand dimensions of the mold required.

Such a mandrel is shown in Fig. 7 which is square in cross section withthe sides tapering slightly throughout the greater portion of its lengthas indicated at 15. Near one end, the mandrel is slightly more tapered,as indicated at 96 and has a small portion adjacent the tapered portionit having sides substantially parallel as indicated at 33.

The final cold drawing step produces a shell or main body portion H ofthe mold as is shown in Figs. 5 and 6 in which I8 corresponds to thetapered sides l5 of the mandrel shown in Fig. 2 and i9 corresponds tothe slightly tapered portion l6 of the mandrel and 20 corresponds to theportion 33 of the mandrel.

In the finished mold, the main body portion ii is provided with asuitable base 26 to form a bottom for the mold cavity and whichcomprises a single copper piece shaped to conform with the crosssectional area of the body portion H of the mold. A projecting squareportion 21 of the base is designed to fit snugly in the portion 20 ofthe body of the mold. The base is mounted on the body of the mold bymeans of straps 22 fixed to the body portion by bolts 23. A hole isprovided in the base and holes 26 are provided in the straps to registerwith said hole in the base. A pin 25 is inserted through these holes tohold the base rigidly in the proper position.

Suitable trunnions 28 are mounted upon the body portion of the mold bymeans of shoulder as which is fixed to the body portion by means ofangles 30 and 3| which are held to the body portion by bolts 32. Thecompleted mold may then be mounted in a cradle in a manner suitable forreceiving the molten metal to be cast. Modifications in the shape of themold may be readily made in accordance with the invention. Onemodification is shown in Fig. 10 in which 50 represents the shell and 5!the cross sectional shape of the mold cavity. This indicates the wideapplication of the method herein described.

It is seen from the foregoing description that the shortcomings of'themethod of forming a copper mold by allowing molten copper, to freezearound a core and then extracting the core are avoided. While thatmethod is commonly practiced, it is disadvantageous in that the roughsurfaces formed by the core must be machined smooth to finisheddimensions. The improved method of the invention avoids this machiningoperation. Further, the old core method produces appreciable percentagesof defective molds due to cracks and blow holes and often these defectsare not visible until after a considerable amount of machinework hasbeen done.

Another method, heretofore commonly employed for forming copper molds,was to bore a solid block of copper to produce the mold cavity. But thismethod is relatively expensive and unless the metal is forged beforeboring a large portion will be found unsound from gas pockets and mustbe discarded after a great deal of time and money has been spent.

Another serious limitation upon the methods heretofore commonlypractised is that molds having a considerable depth and cross sectionother than circular can be produced only with difficulty, if at all.

The present invention avoids all these shortcomings and provides amethod whereby a mold of any desirable depth and of any shape of crosssection may be produced economically and which will stand up after long,hard usage. Expensive and difficult machinery operations are entirelyeliminated while a smooth, accurately dimensioned flawless castingcavity is produced. Hidden flaws and cavities present in the originalmold stock are likewise eliminated. There may be thus made, according tothe invention, a more perfect mold of longer life and more convenientform.

While certain novel features of the invention have been disclosed andare pointed out in the annexed claims, it will be understood thatvarious omissions, substitutions and changes may be made by thoseskilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The method of forming a mold which comprises inserting a hot metalbillet into a receptacle, piercing said billet with a plunger, removingand cold drawing said pierced billet over a smooth mandrel having aconfiguration similar to that desired for the casting cavity in the moldand attaching a bottom to the piece thus formed.

2. The method of forming a mold which comprises piercing a suitable hotcopper billet thereby yielding a mold stock of desired length having acavity therein of uniform cross-section, thereafter drawing said moldstock over a smooth mandrel, the exterior dimensions of which correspondto the desired dimensions of the cavity in the finished mold and closingone end of said mold by securing a copper bottom-piece thereto.

3. In forming a mold having a depth substantially greater than itswidth, the improvement which comprises piercing a hot copper block in apress adapted to yield a mold stock having a cavity of uniformcross-section and thereafter subjecting the stock to successive colddraws over a series of mandrels, the last draw being performed on amandrel possessing the same shape as the cavity desired in the finishedmold.

4. In forming a mold, the improvement which comprises piercing a hotcopper billet and then cold drawing said pierced billet over a smoothmandrel so shaped as to determine the configuration of the castingcavity of the finished mold.

5. The method of forming a mold for vertical casting of metals andalloys which comprises piercing a block of hot copper to form a bodyportion having a uniform cavity therethrough, drawing the pierced bodyportion over mandrels to impart the desired dimensions to the moldcavity and sealing that end of the mold which is on the bottom when saidmold is in position for castof copper or copper alloy in a press to forma, hoiiow shell, removingthe oxide formed on the surfacx of the shell,drawing said shell over a steel mandrel oi. the size and shape of thecasting to be made in said mold and suitably sealing one 5 end 01' themold body.

WILLIAM H. PEIRCE.

